Ukrainian power engineers and scientists became interested in using hydrogen technologies for a long time, more than 30 years ago. The use of hydrogen with gas can significantly improve the environmental friendliness of gas. And pure hydrogen has quite ambitious prospects in general.
In the summer of 2020, RGC was the first to test hydrogen in its own networks. And it attracted scientists to the process.
During the VI Ukrainian Gas Forum, the Eastern European Gas Partnership, held at the end of October, Ukrainian scientists presented the first research results on the use of hydrogen and gas- hydrogen mixtures in networks and household appliances.
Low-pressure networks - pre-suitable for hydrogen
Testing experimental gas networks for tightness when filled with hydrogen showed that sections of medium pressure operating on hydrogen had significant leaks. And they did not meet the requirements of tightness. But the low-pressure areas met these requirements, said Ph.D. Kyryl Kostohryz.
The tests were carried out at test sites, where models of gas networks were installed in full compliance with the existing gas distribution networks.
Researchers found that the pressure drop in medium pressure networks ranged from 0.24 to 0.4% per hour and exceeded the permissible rate by 2.5-4 times.
A leak was recorded in one medium pressure section. The hydrogen concentration was very high there and was approaching the danger line. The leak has been repaired. Further testing showed a significant reduction in pressure drop to 0.09% per hour. That corresponded to the permissible tightness standard for technological gas pipelines.
The pressure drop was insignificant in low-pressure gas pipelines – on average, 0.01% per hour.
Typical fixed leaks are weld seals, even high quality ones. It was unexpected, Kostohryz noted. Also, screwed and muff joints made with modern specialized sealing materials and sensor connection points did not hold hydrogen.
“Based on the research results, it is already possible to formulate the directions of work on the technical re-equipment of distribution networks and the solution of related problems,” Kostohryz said.
The explosive hazard of hydrogen: the threat exaggerated
Ivano-Frankivsk National Technical University’s researchers performed mathematical modeling of the consequences of a hydrogen mixture explosion. They found out that even under the condition of a pressure of 4 kg of 100% hydrogen at a distance of 4 meters, there are no serious consequences for people's life and health. There is a small risk of non-renewable destruction of buildings and structures, said Maksym Karpash, professor at the Institute of Physics and Technology.
The influence of the ambient temperatures on the hydrogen mixture was also significant.
"A temperature change can have a stronger effect than a change in pressure according to the readings of manometers, which is an atypical challenge," said Karpash.
It is necessary to develop and test studies of the influence of various hydrogen concentrations on the quality of odorization (giving the smell of a gas mixture) and research the typical devices used. And separately investigate the problem of micro-leaks of the gas-hydrogen mixture.
Household appliances and hydrogen use
Borys Soroka, head of the department of high-temperature heat and mass transfer at the Gas Institute of the National Academy of Sciences of Ukraine, told about the researchers' results at the Zhytomyr test site, studying the possibility of a hydrogen mixture in household appliances.
The tests were carried out on a household gas stove and a heating boiler. The results showed that 50% hydrogen concentration in methane is optimal for safe combustion.
Concerning the methane-hydrogen mixture's polluting factor, experiments have shown that the higher the hydrogen content in the mixture, the lower the formation of carbon monoxide.
By burning a mixture with hydrogen, the researchers obtained a lower nitric oxide formation than when burning pure natural gas. Moreover, the higher the hydrogen concentration was, the less nitrogen oxide was formed. Until now, science has argued that burning gas without impurities is the cleanest. The researchers attributed this effect to the combustion of hydrogen and the formation of water vapor.
“The first results using a 50% hydrogen/gas mixture are promising. But further research is needed,” Borys Soroka summed up.
Materials for transporting hydrogen
Hryhotii Nikiforchin, a leading researcher at the Karpenko Physico-Mechanical Institute, spoke about the risks of pipeline destruction under the influence of hydrogen.
The results were obtained due to experience in assessing the condition of long-term operating transit gas pipelines.
Nikiforchin explained that even due to the low humidity of the gas, moisture condensation is possible on the inner surface of the pipes, which starts the corrosion process, which is a source of hydrogen. And part of the generated hydrogen is absorbed by the metal in the atomic state and can pass through the entire pipe wall. Even when transporting natural gas, there is a danger of hydrogen saturation in pipes.
When the pipe is also filled with molecular hydrogen, hydrogenation of the pipe wall from the inner surface side is possible in the case of dissociation (decomposition) of molecular hydrogen into atomic hydrogen. Only atomic hydrogen can penetrate and harm the material, the scientist explained.
Whether there is a connection between the first and second hydrogenation mechanisms – the researchers have not figured out yet. But in general, the hydrogenation of pipes harms their reliability. According to the calculations of scientists, the material becomes essentially fragile after 53 years of operation. If there is micro-damage to pipes, this greatly increases the danger of their fragility. And the process of hydrogenation actively contributes to this.
However, if the pipeline's metal has a low sensitivity to hydrogen embrittlement, the negative effect of hydrogen may not appear, the scientist noted.
In general, all speakers agreed that research should be continued. So far, there is still a lot that needs to be found out experimentally and analyzed. In particular, scientists who are working on using hydrogen need to unite their efforts and share the results and conduct joint research.
The researchers also focused on the lack of a regulatory framework in Ukraine to use hydrogen in general and in the gas transmission system. It also needs to be worked out.